This SOW describes the follow-up activities related to the PRIMAVERA-ESCUDDO Trial (?Puente de Respuesta Inmunolgica para Mejorar el Acceso a Vacunas y ERrAdicar el cncer? PRIMAVERA) which is part of the NCI?s Human Papillomavirus (HPV) vaccine evaluation efforts. PRIMAVERA (Task Order #75N91019F00129) is aimed to evaluate the non-inferiority of 1-dose of bivalent HPV vaccine in girls (9-14 years) to 3-doses of quadrivalent vaccine in women (18-25 years) by comparing HPV16/18 antibody levels between the two groups at 24 (interim) and 36 (final) months. This study complements the ongoing large-scale clinical trial ESCUDDO, which evaluates the vaccine efficacy for a 1-dose regimen against virologic outcomes among 24,000-girls in Costa Rica. PRIMAVERA will bolster this evidence by addressing the same research question in a new population using a novel standard arm with parallel study procedures and aims to provide earlier preliminary results to ESCUDDO.